Think Your Probiotics Are Causing Diarrhea? It’s Probably Something Else

Probiotics are a popular supplement these days. Many people take them to improve their gut health. But they may have other health benefits as well, like treating acne or high cholesterol. Probiotics can prevent and treat diarrhea by helping your gut function more effectively. But can probiotics also cause diarrhea as a side effect? Let’s look at what the research shows. 

What are probiotics?

Probiotics are live microorganisms that are used for their health benefits. They’re usually made of live bacteria but can also include yeast. One way to get probiotics is through your diet. Fermented foods (like yogurt or sauerkraut) are naturally high in probiotics. You can also get probiotics as a dietary supplement. 

How probiotics work in the body

People often think of germs as a bad thing. And sometimes they do cause infections. But there are good germs, too. Those are the microorganisms that line our digestive tract. These organisms help you:

• Digest and absorb food

• Regulate our immune system

• Prevent other bacteria from causing disease 

• Produce vitamins like vitamin B12 and vitamin K

Probiotic products have microorganisms that are like the ones in our gut. When you take probiotics, they go to your gut and help increase the number of helpful microorganisms. 

Can probiotics cause diarrhea?

Probably not. Some people report soft stools or stomach upset when they start probiotics. But large studies have shown that people taking probiotics don’t have more gastrointestinal symptoms compared with people not taking probiotics. 

So what does that mean if you take probiotics and have diarrhea? Most likely the diarrhea isn’t related to the probiotics at all. In a review of 31 studies, the most common side effects people reported were stomach cramping, soft stools, and gas. However, those who took probiotics had a 17% lower chance of experiencing these side effects compared with those who took placebo pills.

Keep in mind that probiotics are sometimes used to treat constipation. If you’re constipated, probiotics can help you poop more often, and make your stools softer. So if you have constipation, you might feel that probiotics are causing diarrhea. But they actually help you have more normal stools.

What are the benefits of taking probiotic supplements?

We’re still learning about the different benefits of probiotics. Research shows that probiotics:

• Prevent antibiotic-associated diarrhea

• Prevent Clostridioides difficile (C. diff) colitis

• Help treat irritable bowel syndrome (IBS)

• Lower the risk for allergies and eczema

• Help with lactose intolerance

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Probiotics are being studied as a possible treatment to help with many other conditions, ranging from obesity to the common cold. 

What is the best way to take probiotics?

The best way to take probiotics might depend on what kind of strains are in your probiotic. Some probiotics should be taken on an empty stomach while others are recommended to take with meals. 

Stomach acids can break down the probiotics before they get to the gut. Many formulations now use a special coating so that the probiotics can survive stomach acids and reach the gut. For this reason, tablets and capsules may be more effective than powders and drinks overall.   

One study found that probiotics were the least effective if used 30 minutes after a meal. This same study, however, found that the Saccharomyces boulardii strain wasn’t affected by the timing of meals. So it’s best to follow the manufacturer's instructions about the best time to take your probiotics. 

Can you take too many probiotics? 

The American Academy of Family Physicians (AAFP) recommends a dose of: 

• 5 to 10 billion colony-forming-units (CFUs) per day for children

• 10 to 20 CFUs per day for adults. 

Probiotics are safe for most people, so a higher dose isn’t harmful, according to research. But the AAFP recommends staying within these ranges because those are the ranges that have been studied well. 

Some people have wondered if taking too many types of probiotics can be harmful, or make the probiotics less effective. In some cases, a single strain of bacteria seemed more effective than multiple strains given together. Other studies suggest that using multiple strains of probiotics might be better. Most of the time, single or multiple strains of probiotics seem to be similar in how well they work. More research needs to be done to get a good answer to this question. 

If you have a weakened immune system, you should talk with a healthcare provider about doses and dosages before taking probiotics. This is because in rare cases, probiotics can increase the risk of infection.

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Written by:

Karen Hovav, MD, FAAP

Karen Hovav, MD, FAAP, has more than 15 years of experience as an attending pediatrician. She has worked in a large academic center in an urban city, a small community hospital, a private practice, and an urgent care clinic.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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